Genetics Notes

Amoeba Sisters Notes

• heredity - how traits are passed from parents to offspring

• genes can be influenced by environment sometimes

• DNA code is in most of your cells

• Deoxyribonucleic Acid - DNA

• Nucleic Acids are made of Nucleotides

  • 
  • The only area where parts change in the Nucleotide is the base **__most important__
  • Adenine (A)
  • Guanine (G)
  • Cytosine (C)
  • Thymine (T)
  • A__pples in the Tree, Car in the G__arage
  • amount of bases and the combo of bases change
  • bases are held together in hydrogen bonds

• DNA held together in a double helix

• Genes - specific portion of DNA that gives you a certain trait

• DNA is the cookbook - Genes are the recipe

• Genes can be turned on and off - gene regulation

Week 24 Notebook Check: Genetics and Meiosis

Key Words

• reproduction - making one or more organisms from 2 parents
• gametogenesis - a process producing gametes (meiosis)
• $**sexual reproduction** - gametes join together to form an organism$
  • $**gametes** - ONLY sex cells (egg/sperm)$
• $**asexual reproduction** - organisms are made from one parent$
  • $**binary fission** - type of asexual reproduction$
  • $happens in prokaryotes$
• %%somatic cell - any cell that is not a sex cell%%
• %%germ cell - the cell that is made when egg is fertilized by sperm%%
• zygote - fertilized eggs w/ a set of chromosomes from each parent

Environment Affects Reproduction

• sexual reproduction is better in changing environments
• asexual reproduction is optimal for stagnant conditions

3 Types of Mitotic Reproduction (for Eukaryotes)

1. Budding - forms a new organism from a small projection growing on the surface
2. Fragmentation - splitting the parent to both grow into a new organisms
3. Vegetative Reproduction - forms a new plants from the modification of a stem or underground structure on the parent plant

Diploid vs. Haploid

Diploid

• somatic cell (liver, skin, heart cells)
• diploid cells come from mitosis

Haploid

• gametes
• one chromosome copy
• haploid cells come from meiosis

• chromosome numbers have to be maintained in animals.

Autosomes & Sex Chromosomes

• body has 23 pairs of chromosomes
• chromosome pairs 1-22 are autosomes
• pair 23 determines gender (XX, XY) (sex chromosomes)
  • unfertilized egg - X
  • sperm - X or Y
• homologous pairs - pairs of chromosomes are the same size/shape

• during meiosis, there are two divisions that end up with 4 haploid cells
• germ cell - the cell that is made when egg is fertilized by sperm

Meiosis 1

• happens after DNA has been replicated (synthesis)

Prophase 1

• double the amount of chromosomes

Metaphase 1

• mom and dad’s cells line up on the cell equator separately

Anaphase 1

• mom and dad chromosomes move away from each other

Telophase 1

• spindle fibers fade away; cytokinesis occurs forming 2 diploid cells

Meiosis 2

• this takes the cells split in Meiosis 1 in half
• same cycle happens, but happens in 2 different cells (diploid) - ending up with 4 cells (diploid)

2/10 Class Notes

• The mother can pass on genetic diseases through her gametes.
• nondisjunction - not able to split

Additions for Weeks 25-27 (Notebook Check)

Crossing Over/Genetic Variation

• homologous chromosomes are attached together by a protein called the synaptonemal complex
• mutations create different versions of genes called alleles
• moving around alleles during reproduction causes genetic variation
• how chromosomes act during meiosis and fertilization determines a lot of mutations/variations
• 3 factors in genetic variation
  • independent assortment of chromosomes
  • homologous chromosomes align randomly in metaphase as shown below
  • during independent assortment - chromosomes are sorted between maternal and paternal homologues into daughter cells independently of the other pairs
    • 
  • crossing over
  • crossing over is how genetic mutation occurs, basically two chromosomes change parts
  • crossing over makes recombinant chromosomes - combining genes received from each parent
  • happens in prophase 1
  • contributes to variation because genes from each parent are combined into one chromosome
  • random fertilization
  • contributes to variation because any sperm could fuse with any ovum

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Week 26 Notebook Check: Mendelian Genetics

1. Body ⬇
2. Cells ⬇
3. Chromosomes ⬇
4. DNA ⬇
5. Genes

Vocab for the Chapter

NOTE: (some of these were hard to rewrite - so I sometimes added on to the terms or copy-and-pasted from the slideshow and are further explained later)

• gene - a unit of heredity; a section of DNA sequence encoding a single protein
• genome - the entire set of genes in an organism
• alleles - two genes that occupy the same position on homologous chromosomes and that cover the same trait (like ‘flavors’ of a trait). [ex. eye color or hair type]
• locus - a fixed location on a strand of DNA where a gene or one of its alleles is located
• homozygous - having the same genes for one trait for each parent
• heterozygous - having 2 different genes for a single trait (ex. having a green eye gene and a blue eye gene)
• dominant - masks recessive genes / will show in heterozygous and homozygous conditions (GG, Gg)
• recessive - will be covered by dominant genes / shows only in homozygous conditions (gg)
• hybridization - mating 2 organisms with different genes for a trait
• genotype - genetic makeup of organisms
• phenotype - physical appearance of an organism (genotype + environment)
• monohybrid cross - a genetic cross involving a single pair of genes (one trait); parents differ by a single trait
• dihybrid cross - a genetic cross where parents have two traits that are different
• test cross - cross with a homozygous recessive individual

Mendel / his Pea Plants & findings

Pea Plants

• Looked at 7 characteristics for his experiments

1. Round vs. Wrinkled
2. Yellow vs. Green
3. Purple vs. White Petals
4. Inflated vs. Pinched Pods
5. Green vs. Yellow Pods
6. Axial vs. Terminal Flowers
7. Long vs. Short Stems

Mendelian Crosses

• used hybridization (see vocab section for anything in bold) / this involved putting pollen within another plant’s stigma

Monohybrid Cross

• parents only have one trait that is different (same species)
• P = parental generation
• F₁ = first filial generation from genetic cross
• F₂ = second filial generation - offspring of F₁
• ex: tall vs short stems
  • T (tall) + t (short) = Tt
  • Punnett square for F₁
  • 100% heterozygous
  • 100% dominant

• Example of the F₂ generation
  • 50% homozygous / 50% heterozygous
  • 75% dominant / 25% recessive

Dihybrid Cross

• parents have two traits that are different
• ex. flower color and stem length
  • P (purple flower) / p (white flower)
  • T (tall) / t (short)
  • TT + PP (tall, purple) x tt + pp (short, white)
  • F₁ will be tall and purple

• F₂ Punnett Square (TP, Tp, tP, tp)
• Tall, purple (9); Tall, white (3); Short, purple (3); Short, white (1)

Test Cross

• when you cross with with a homozygous recessive individual to figure out the genotype of the other thing
  • 100% purple means the genotype of the unknown flower is PP

• 50% purple means genotype is Pp

Mendel’s Principles

1. Principle of Dominance - one allele masked another, one allele was dominant over the other in the F1 generation
2. Principle of Segregation - when gametes are formed, the pairs of hereditary factors (genes) become separated, so that each sex cell (egg/sperm) receives only one kind of gene.
3. Principle of Independent Assortment - “Members of one gene pair segregate independently from other gene pairs during gamete formation”

1. genes get switched around - a benefit to sexual reproduction